Nonmagnetic ground state of marcasite FeTe₂: The competition between crystal field splitting and on-site Coulomb repulsion

The magnetic ground states in crystalline systems are significant for both fundamental condensed-matter physics and practical materials engineering. Marcasite FeTe₂, characterized as a small-gap semiconductor, exhibits anomalous magnetic behaviors in low-temperature experiments. In this study, first-principles density-functional theory calculations combined with scanning-tunneling microscopy/spectroscopy are employed to investigate the magnetic ground state of marcasite FeTe₂. It is revealed that the competition between crystal-field splitting and on-site Coulomb repulsion plays the key role in the formation of localized magnetic moments in FeTe₂. The ground state of FeTe₂ bulk is confirmed to be nonmagnetic, while the magnetic responses of FeTe₂ observed at low temperatures are suggested to be related to the magnetic Fe atoms on the crystal surfaces. Our work proposes a straightforward competing mechanism for determining ground-state magnetism of various localized-moment crystalline systems.